var promise = new Promise(function (resolve, reject) {
    if () {  //异步操作成功
        resolve(value);
    } else {
        reject(error);
    }
});

promise.then(
    function (value) {
        //success成功
    },
    function (error) {
        //failure失败
    });

function timeOut(ms) {
    return new Promise(function (resolve, reject) {
        return setTimeout(resolve, ms, "done");
    });
}

timeOut(3000).then(function (value) {
    console.log(value);
});

let promise = new Promise(function (resolve, reject) {
    console.log('Promise');
    resolve();
});

promise.then(function () {
    console.log('resolved.');
});

console.log('Hi!');
// Promise
// Hi!
// resolved